Well when you raised the poundage from 60 to 70 you signifigantly decreased the brace height of the bow. This decrease in brace height also pushed the cables foward. The cables being more foward pushed your MZE down more so now when you draw the bow the MZE is starting out lower and not stopping as high as it did before you adjusted the poundage.

So with the MZE arm sitting lower at full draw the arrows are pointing downward and thus hitting lower on your target.

To remedy this problem you need to remove the arm from the cable clamp and unscrew it one full turn at a time until the stop screw is again just making contact with the stop plate.